Multiple emulsion systems (broadly defined as systems in which water/oil and oil/water emulsion co-exist) are very valuable because these permit incorporation and enhanced delivery of benefit agents. Thus, these multiple emulsions have been used for many years, for example, in cosmetic and pharmaceutical areas to deliver cosmetic or pharmacological benefit agents (see for Example, U.S. Pat. No. 5,306,498 to Vesperini; or U.S. Pat. No. 5,567,426 to Nadaud et al.). The level of high HLB (&gt;10) cleansing surfactant in almost all the cosmetic and pharmaceutical art referred to above is below 5% by wt. of the compositions. If the high HLB surfactant concentration in the above referred to art were significantly increased, the multiple emulsion droplets would become less and less stable, leading to phase separation. In U.S. Pat. Nos. 5,656,280 and 5,589,177 to Herb et al, the multiple emulsion droplets are stabilized in high levels of conditioning surfactants which form lamellar liquid crystals.
In applicants' copending application entitled "Stable Multiple Emulsion Composition" and filed on same date as the subject application, applicants found multiple emulsion systems which employed surfactant systems which were in an isotropic phase which at the same time did not rapidly destabilize the multiple emulsion droplets. It is particularly advantageous to use surfactant systems which are isotropic because these systems provide improved foam/lather and because they can be formed using a much wider range of surfactant.
While the final compositions of that invention are microscopically stable in that the multiple emulsion droplets maintain their integrity, they phase separate over time. In the subject invention, the compositions do not phase separate due to specific selection of an external surfactant system in combination with a stabilizing natural gum polymer which forms a gelled external aqueous phase with a relatively high concentration of surfactant. Compositions which employ similar technology (i.e. gelled external aqueous phase) are described in U.S. Pat. No. 5,306,498 to Vesperini, U.S. Pat. No. 4,083,798 to Versteeg, U.S. Pat. No. 5,332,595 to Gaonkar, U.S. Pat. Nos. 5,576,064 and 5,656,263 both to Fructus, and U.S. Pat. No. 5,567,426 to Nadaud. In all of these aforementioned compositions, however, the level of high HLB external surfactant was in one case only 5% and in most cases zero.
It is the object of this invention to provide a gelled isotropic external surfactant phase which contains high levels of surfactant where the integrity of the multiple emulsion droplet is maintained and the composition does not phase separate.